Please refer to the following
Type installed on the ceiling
In the case of a type installed on the ceiling, you can disconnect by turning the cover counterclockwise.
Type installed on the wall
In the case of the type installed on the wall, you can remove the cover by removing the screw at the top of the cover.
Below in an example of remove of Type installed on the wall
For the following types, you can remove the light bulb from the top without removing the cover